We wish to use an integrated set of ultrastructural, biochemical, and genetic methods to study the site specific replication of the cell surface of Streptococcus faecalis. An apparent single equatorial growth point indicated by the presence of an external marker which separates cell surface made in one generation from that made in another, and the absence of surface turnover will be used in testing a model of envelope replication. This model states that both cross wall and peripheral wall are produced through a unitary mechanism involving 1) the linear growth of the leading edge of the cross wall and 2) the subsequent controlled separation of the cross wall into two layers of peripheral wall. Ultrastructural and biochemical methods have been evolved to quantitatively describe both the extension and separation aspects of the model, while genetic, physiological and metabolic inhibition techniques will be used to dissect its regulation in steady state and synchronized populations.